Asymmetrical multi-gate string driver for memory device

ABSTRACT

Some embodiments include apparatuses, and methods of operating the apparatuses. Some of the apparatuses include a first group of conductive materials interleaved with a first group of dielectric materials, a first pillar extending through the first group of conductive materials and the first group of dielectric materials, memory cells located along the first pillar, a conductive contact coupled to one of the conductive materials, and a second pillar extending through a second group of conductive materials and a second group of dielectric materials. The second pillar includes a first portion coupled to a conductive region, a second portion, and a third portion, and a fourth portion coupled to the conductive contact. The second portion is located between the first and third portions. The second portion has a doping concentration less than a doping concentration of each of the first and fourth portions.

BACKGROUND

Memory devices are widely used in computers, cellular phones, and manyother electronic items. A conventional memory device, such as a 3D(three-dimensional) flash memory device, has many memory cells to storeinformation. A memory device has conductive lines and circuitry toprovide voltages to the conductive lines in order to access the memorycells during different memory operations. Such circuitry often includesdrivers (e.g., switches) to pass voltages from a voltage source torespective conductive lines. Some memory operations may use a relativelyhigh voltage (e.g., ten to 20 times the operating voltage of the memorydevice). Many conventional drivers are designed to sustain such a highvoltage. However, some memory devices may use even higher voltage insome of their operations. Such a higher voltage may make someconventional drivers unreliable. Designing drivers to support such ahigher voltage may add complexity to peripheral circuitry associatedwith conventional drivers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an apparatus in the form of a memorydevice, according to some embodiments described herein.

FIG. 2 shows a block diagram of a portion of a memory device includingmemory cell strings and drivers (e.g., driver circuits), according tosome embodiments described herein.

FIG. 3 shows a side view of a structure of a portion of the memorydevice of FIG. 2, according to some embodiments described herein.

FIG. 4 shows a top view of a structure of the portion of the memorydevice of FIG. 3, according to some embodiments described herein.

FIG. 5 shows a structure of a portion of a driver of the memory deviceof FIG. 2, FIG. 3, and FIG. 4, according to some embodiments describedherein.

FIG. 6 shows a structure of a portion of a driver, which can be avariation of the driver of FIG. 5, according to some embodimentsdescribed herein.

FIG. 7 shows a structure of a portion of a driver, which can be anothervariation of driver of FIG. 5, according to some embodiments describedherein.

FIG. 8 shows a structure of a portion of a driver, which can be avariation of the driver of FIG. 7, according to some embodimentsdescribed herein.

DETAILED DESCRIPTION

FIG. 1 shows a block diagram of an apparatus in the form of a memorydevice 100, according to some embodiments described herein. Memorydevice 100 can include a memory array (or multiple memory arrays) 101containing memory cells 102 arranged in blocks (blocks of memory cells),such as blocks BLK0 and BLK1. Each of blocks BLK0 and BLK1 can includeits own sub-blocks, such as sub-blocks SB0 and SB1. In the physicalstructure of memory device 100, memory cells 102 can be arrangedvertically (e.g., stacked over each other) over a substrate (e.g., asemiconductor substrate) of memory device 100. FIG. 1 shows memorydevice 100 having two blocks BLK0 and BLK1 and two sub-blocks in each ofthe blocks as an example. Memory device 100 can have more than twoblocks and more than two sub-blocks in each of the blocks.

As shown in FIG. 1, memory device 100 can include access lines (whichcan include word lines) 150 and data lines (which can include bit lines)170. Access lines 150 can carry signals (e.g., word line signals) WL0through WLm. Data lines 170 can carry signals (e.g., bit line signals)BL0 through BLn. Memory device 100 can use access lines 150 toselectively access memory cells 102 of blocks BLK0 and BLK1 and datalines 170 to selectively exchange information (e.g., data) with memorycells 102 of blocks BLK0 and BLK1.

Memory device 100 can include an address register 107 to receive addressinformation (e.g., address signals) ADDR on lines (e.g., address lines)103. Memory device 100 can include row access circuitry 108 and columnaccess circuitry 109 that can decode address information from addressregister 107. Based on decoded address information, memory device 100can determine which memory cells 102 of which sub-blocks of blocks BLK0and BLK1 are to be accessed during a memory operation. Memory device 100can include drivers (driver circuits) 140, which can be part of rowaccess circuitry 108. Drivers 140 can include the drivers described inmore detail with reference to FIG. 2 through FIG. 8. Drivers 140 canoperate (e.g., operate as switches) to form (or not to form) conductivepaths (e.g., current paths) between nodes providing voltages andrespective access lines 150 during operations of memory device 100.

Memory device 100 can perform a read operation to read (e.g., sense)information (e.g., previously stored information) from memory cells 102of blocks BLK0 and BLK1, or a write (e.g., programming) operation tostore (e.g., program) information in memory cells 102 of blocks BLK0 andBLK1. Memory device 100 can use data lines 170 associated with signalsBL0 through BLn to provide information to be stored in memory cells 102or obtain information read (e.g., sensed) from memory cells 102. Memorydevice 100 can also perform an erase operation to erase information fromsome or all of memory cells 102 of blocks BLK0 and BLK1.

Memory device 100 can include a control unit 118 that can be configuredto control memory operations of memory device 100 based on controlsignals on lines 104. Examples of the control signals on lines 104include one or more clock signals and other signals (e.g., a chip enablesignal CE #, a write enable signal WE #) to indicate which operation(e.g., read, write, or erase operation) memory device 100 can perform.

Memory device 100 can include sense and buffer circuitry 120 that caninclude components such as sense amplifiers and page buffer circuits(e.g., data latches). Sense and buffer circuitry 120 can respond tosignals BL_SEL0 through BL_SELn from column access circuitry 109. Senseand buffer circuitry 120 can be configured to determine (e.g., bysensing) the value of information read from memory cells 102 (e.g.,during a read operation) of blocks BLK0 and BLK1 and provide the valueof the information to lines (e.g., global data lines) 175. Sense andbuffer circuitry 120 can also be configured to use signals on lines 175to determine the value of information to be stored (e.g., programmed) inmemory cells 102 of blocks BLK0 and BLK1 (e.g., during a writeoperation) based on the values (e.g., voltage values) of signals onlines 175 (e.g., during a write operation).

Memory device 100 can include input/output (I/O) circuitry 117 toexchange information between memory cells 102 of blocks BLK0 and BLK1and lines (e.g., I/O lines) 105. Signals DQ0 through DQN on lines 105can represent information read from or stored in memory cells 102 ofblocks BLK0 and BLK1. Lines 105 can include nodes within memory device100 or pins (or solder balls) on a package where memory device 100 canreside. Other devices external to memory device 100 (e.g., a memorycontroller or a processor) can communicate with memory device 100through lines 103, 104, and 105.

Memory device 100 can receive a supply voltage, including supplyvoltages Vcc and Vss. Supply voltage Vss can operate at a groundpotential (e.g., having a value of approximately zero volts). Supplyvoltage Vcc can include an external voltage supplied to memory device100 from an external power source such as a battery or alternatingcurrent to direct current (AC-DC) converter circuitry.

Each of memory cells 102 can be programmed to store informationrepresenting a value of at most one bit (e.g., a single bit), or a valueof multiple bits such as two, three, four, or another number of bits.For example, each of memory cells 102 can be programmed to storeinformation representing a binary value “0” or “1” of a single bit. Thesingle bit per cell is sometimes called a single-level cell. In anotherexample, each of memory cells 102 can be programmed to store informationrepresenting a value for multiple bits, such as one of four possiblevalues “00”, “01”, “10”, and “11” of two bits, one of eight possiblevalues “000”, “001”, “010”, “011”, “100”, “101”, “110”, and “111” ofthree bits, or one of other values of another number of multiple bits. Acell that has the ability to store multiple bits is sometimes called amulti-level cell (or multi-state cell).

Memory device 100 can include a non-volatile memory device, and memorycells 102 can include non-volatile memory cells, such that memory cells102 can retain information stored thereon when power (e.g., voltage Vcc,Vss, or both) is disconnected from memory device 100. For example,memory device 100 can be a flash memory device, such as a NAND flash(e.g., 3-dimensional (3-D) NAND) or a NOR flash memory device, oranother kind of memory device, such as a variable resistance memorydevice (e.g., a phase change memory device or a resistive Random AccessMemory (RAM) device.

One of ordinary skill in the art may recognize that memory device 100may include other components, several of which are not shown in FIG. 1so as not to obscure the example embodiments described herein. At leasta portion of memory device 100 can include structures and performoperations similar to or identical to the structures and operations ofany of the memory devices described below with reference to FIG. 2through FIG. 8.

FIG. 2 shows a block diagram of a portion of a memory device 200including memory cell strings 231 and 232 and drivers (e.g., drivercircuits) 240, 241, 242, and 243, according to some embodimentsdescribed herein. Memory device 200 can correspond to memory device 100of FIG. 1. For example, memory cell strings 231 and 232 can be part of amemory array of FIG. 2 that can correspond to memory array 101 of FIG.1, and drivers 240, 241, 242, and 243 can correspond to drivers 140 ofFIG. 1.

Memory device 200 can include a data line 270 that carry a signal (e.g.,bit line signal) BL0. Data line 270 can be structured as a conductiveline (which includes conductive material). The memory cell strings 231and 232 can share data line 270. FIG. 2 shows an example of one dataline 270 of memory device 200. However, memory device 200 can includenumerous data lines.

Memory device 200 can include a line 299 that can carry a signal SRC(e.g., source line signal). Line 299 can be structured as a conductiveline (which includes conductive materials) and can form part of a source(e.g., a source line) of memory device 200.

As shown in FIG. 2, memory device 200 can include memory cells 210, 211,212, and 213; select gates (e.g., drain select gates or transistors) 261and 262; and select gates (e.g., source select gates or transistors)260. Memory device 200 can include select lines (e.g., drain selectlines) 281 and 282 to control (e.g., turn on or turn off) select gates261 and 262, respectively, and a select line (e.g., source select line)280 to control (e.g., turn on or turn off) select gates 260.

Each of memory cell strings 231 and 232 can include one of memory cells210, one of memory cells 211, one of memory cells 212, and one of memorycells 213. Memory cells 210, 211, 212, and 213 in a respective memorycell string are coupled in series between a respective drain select gate(e.g., select gate 261 or 262) and a respective source select gates(e.g., one of select gates 260).

FIG. 2 shows an example of four memory cells 210, 211, 212, and 213 ineach memory cell string. The number of memory cells in each of memorycell strings 231 and 232 can vary. FIG. 2 shows an example of two memorycell strings and associated select gates (e.g., drain and source selectgates) coupled between data line 270 and line 299 to help focus on theembodiments described herein. However, memory device 200 can includenumerous memory cell strings and their select gates coupled between dataline 270 and line 299.

Memory device 200 can include access lines 220, 221, 222, and 223, whichcan be local access lines (e.g., a group of local word lines) that cancarry corresponding signals (e.g., local word line signals) WL0 ₀, WL1₀, WL2 ₀, and WL3 ₀.

Memory device 200 can include access lines 220′, 221′, 222′, and 223′,which can be global access lines (e.g., a group of global word lines)that can carry corresponding signals (e.g., global word line signals)V0, V1, V2, and V3. Signals V0, V1, V2, and V3 can be provided withdifferent voltages or with the same voltage at a particular time,depending on which operation memory device 200 operates at thatparticular time.

As shown in FIG. 2, drivers 240, 241, 242, and 243 can be coupled tobetween respective access lines 220, 221, 222, and 223 and respectiveaccess lines 220′. Each of drivers 240, 241, 242, and 243 can operate asa switch that can be turned on (e.g., placed in a conductive state (oron-state))) or turned off (e.g., placed in a non-conductive state (oroff-state)). Drivers 240, 241, 242, and 243 can be configured to turn onin order to form conductive paths (e.g., current paths) betweenrespective access lines 220, 221, 222, and 223 and 220′, 221′, 222′, and223′. For example, drivers 240, 241, 242, and 243 can be turned onduring read and write operations of memory device 200 when memory cellstring 231 or 232 is selected to store information in or readinformation from a selected memory cell (or memory cells) of memory cellstring 231 or 232,

Drivers 240, 241, 242, and 243 can be configured to turn off in order tonot form conductive paths (e.g., current paths) between respectiveaccess lines 220, 221, 222, and 223 and 220′, 221′, 222′, and 223′. Forexample, drivers 240, 241, 242, and 243 can be turned off when memorycell string 231 or 232 is not selected to store information in or readinformation from a selected memory cell (or memory cells) in memory cellstring 231 or 232.

As shown in FIG. 2, each of drivers 240, 241, 242, and 243 can includecontrol gates (multiple control gates) 251, 252, 253, 254, 255, and 256.Drivers 240, 241, 242, and 243 can share control gates 251 through 256,such that signals (e.g., control signals or voltages) CG1, CG2, CG3,CG4, CG5, and CG6 (shown in FIG. 3) provided to control gates 251through 256, respectively, can be used to concurrently control (e.g.,simultaneously turn on or simultaneously turn off) drivers 240, 241,242, and 243. FIG. 2 shows an example where each of drivers 240, 241,242, and 243 can include six control gates (e.g., 251, 252, 253, 254,255, and 256). However, the number of control gates can vary. Forexample, each of drivers 240, 241, 242, and 243 can include only twocontrol gates and two associated signals to control the two controlgates. In another example, each of drivers 240, 241, 242, and 243 caninclude three or more control gates and associated control signals.

As shown in FIG. 2, memory device 200 can include gate control circuitry247 to provide different sets of voltages to control gates 251 through256. For example, gate control circuitry 247 can provide a set ofvoltages to respective signals CG1, CG2, CG3, CG4, CG5, and CG6 (shownin FIG. 3) to concurrently turn on drivers 240, 241, 242, and 243, andanother set of voltages to signals CG1, CG2, CG3, CG4, CG5, and CG6 toconcurrently turn off drivers 240, 241, 242, and 243.

Drivers 240, 241, 242, and 243 can provide (e.g., drive or pass) signals(e.g., voltages) V0, V1, V2, and V3 from respective access lines 220′,221′, 222′, and 223′ to respective access lines 220, 221, 222, and 223when drivers 240, 241, 242, and 243 are turned on. Drivers 240, 241,242, and 243 do not provide signals V0, V1, V2, and V3 to respectiveaccess lines 220, 221, 222, and 223 when drivers 240, 241, 242, and 243are turned off.

Memory device 200 can include voltage control circuitry 248 to controlthe values of voltages provided by signals V0, V1, V2, and V3 to accesslines 220, 221, 222, and 223. The values of voltages provided by signalsV0, V1, V2, and V3 can be different from each other during an operation(e.g., read or write operation) of memory device 200. As an example, ina read operation of memory device 200, if memory cell 212 of memory cellstring 231 is selected to be read (e.g., to sense information frommemory cell 212 of memory cell string 231), then the voltage applied toaccess line 222 (associated with signal WL2) can have one value (e.g., avalue equal to a read voltage Vread (e.g., V2=Vread)), and the value ofvoltages applied to access lines 220, 221, and 223 can be the same(e.g., V0=V1=V3) but can be different from the value of voltage Vread(e.g., V2<V0, V2, V3). In another example, in a write (e.g., programoperation) of memory device 200, if memory cell 212 of memory cellstring 231 is selected to store information, then the voltage applied toaccess line 222 (associated with signal WL2) can have one value (e.g., avalue equal to a program voltage Vprg (e.g., V2=Vprg (e.g., 30V)), andthe value of voltages applied to access lines 220, 221, and 223 can bethe same (e.g., V0=V1=V3) but can be different from the value of voltageV2 (e.g., V2>V0, V1, V3). Thus, the values of voltages provided bysignals V0, V1, V2, and V3 to access lines 220, 221, 222, and 223(through respective pillars 240 p, 241 p, 242 p, and 243 p) can bedifferent between operations (e.g., between read and write operations)of memory device 200.

During an erase operation of memory device 200 to erase information frommemory cell strings 231 and 232, an erase voltage (e.g., Verase ofapproximately 30V) can be applied to data line 270 and line 299, andaccess lines 220, 221, 222, and 223 can be applied with zero volts.During an erase operation of memory device 200 to erase information fromother memory cell strings that share data line 270 the erase voltage mayalso be applied to data line 270 and line 299 however, access lines 220,221, 222, and 223 can be place in a float condition (or alternatively beapplied with some voltages (through pillars 240 p, 241 p, 242 p, and 243p).

In the physical structures of drivers 240 (as described in more detailwith reference to FIG. 3 through FIG. 8), each of pillars 240 p, 241 p,242 p, and 243 p can include different portions coupled between arespective local access line (e.g., one of access lines 220, 221, 222,and 223) and a respective global access line (e.g., one of lines 220′through 223′). For example, as shown in FIG. 2, pillar 240 p can includeportions 240 d, 240 a, 240 b, and 240 s. Portions 240 d, 240 a 240 b,and 240 s can be parts of the drain, a lightly doped portion relative tothe drain, the body (e.g., channel), and the source, respectively, ofpillar 240 p. In the physical structures of driver 240, it can include apillar (e.g., a vertical pillar) 240 p where portions 240 d, 240 b, and240 s can be portions of pillar 240 p. In FIG. 2, driver 240 can form aconductive path between access lines 220 and 220′ through portions 240d, 240 a, 240 b, and 240 s when driver 240 is turned on. Pillar 240 pdoes not form a conductive path between access lines 220 and 220′ whendriver 240 is turned off.

Each of drivers 241 through 243 can include elements (e.g., a pillar andassociated portions) similar to the elements of driver 240. For example,driver 241 can include pillar 241 p that can include portions 241 d, 241a, 241 b, and 241 s. Driver 242 can include pillar 242 p that caninclude portions 242 d, 242 a, 242 b, and 242 s. Driver 243 can includepillar 243 p that can include portions 243 d, 243 a, 243 b, and 243 s.

FIG. 3 shows a side view of a structure of a portion of memory device200, according to some embodiments described herein. The structure ofmemory device 200 in FIG. 3 corresponds to part of the schematic diagramof memory device 200 shown in FIG. 2. As shown in FIG. 3, memory device200 can include a substrate 390 over which memory cells 210, 211, 212,and 213 of memory cell strings 231 and 232 can be formed in differentlevels (internal levels) over substrate 390 (e.g., formed vertically inz-direction with respect to line 299 and substrate 390).

Substrate 390 of memory device 200 can include monocrystalline (alsoreferred to as single-crystal) semiconductor material. For example,substrate 390 can include monocrystalline silicon (also referred to assingle-crystal silicon). The monocrystalline semiconductor material ofsubstrate 390 can include impurities, such that substrate 390 can have aspecific conductivity type (e.g., n-type or p-type).

Gate control circuitry 247 and voltage control circuitry 248 can beformed in substrate 390. Although not shown in FIG. 3, substrate 390 caninclude circuitry (that can be located under line 299). Such circuitrycan include sense amplifiers, buffers (e.g., page buffers), decoders,and other circuit components of memory device 200.

As shown in FIG. 3, data line 270 can have a length extending in thex-direction, which is perpendicular to the z-direction. Data line 270can include a conductive material (e.g., conductively dopedpolycrystalline silicon (doped polysilicon), metals, or other conductivematerials). Line 299 can include a conductive material and can have alength extending in the x-direction. FIG. 3 shows an example where line299 (e.g., source) can be formed over a portion of substrate 390 (e.g.,by depositing a conductive material over substrate 390). Alternatively,line 299 can be formed in or formed on a portion of substrate 390 (e.g.,by doping a portion of substrate 390). In another alternative structureof memory device 200, line 299 can be form over a dielectric material(e.g., an oxide material over substrate 390.

Select line (e.g., drain select line) 281 and 282 can be located in alevel between data line 270 and memory cell strings 231 and 232. Selectline (e.g., source select line) 280 can be located in a level betweenmemory cell strings 231 and 232 and line 299 (and substrate 390).

Memory cells 210, 211, 212, and 213 of memory cell strings 231 and 232can be located in respective levels between the level of select lines281 and 282 and the level of select line 280. Access lines 220, 221,222, and 223 (associated with memory cells 210, 211, 212, and 213,respectively) can be located in the same levels as memory cells 210,211, 212, and 213, respectively.

Access lines 220, 221, 222, and 223 can include conductive materials (agroup of conductive materials), which can include conductively dopedpolysilicon, metals, or other conductive materials. Memory device 200can include dielectric materials (e.g., not labeled), interleaved with(located in the spaces between) access lines 220, 221, 222, and 223.Examples of such dielectric materials include silicon dioxide. Thematerials of select lines 280, 281, and 282 can include conductivelydoped polysilicon, metals, or other conductive materials and can be thesame as the conductive material of access lines 220, 221, 222, and 223.

As shown in FIG. 3, memory device 200 can include pillars (memory cellpillars) 331 and 332. Each of pillars 331 and 332 can have lengthextending in the z-direction (e.g., extending vertically with respect tosubstrate 390) through access lines 220, 221, 222, and 223 and throughthe dielectric materials (e.g., silicon dioxide) that are interleavedwith access lines 220, 221, 222, and 223. Each of pillars 331 and 332can contact a conductive region of the material that forms part of dataline 270 and contact a conductive region of the material that forms partof line 299.

Each of pillars 331 and 332 can include a material (or materials) toform a conductive path (e.g., a current path) between data line 270 andline 299. Such a material (e.g., undoped or doped polysilicon) of eachof pillars 331 and 332 can be part of a channel (not shown in FIG. 3) ofa respective pillar among pillars 331 and 332.

For simplicity, FIG. 3 omits detailed structures of memory cells 210,211, 212, and 213. However, memory cells 210, 211, 212, and 213 caninclude structures of a 3D NAND memory device or other non-volatilememory devices. For example, memory cells 210, 211, 212, and 213 caninclude a TANOS (TaN, Al₂O₃, Si₃N₄, SiO₂, Si) structure, a SONOS (Si,SiO₂, Si₃N₄, SiO₂, Si) structure, a floating gate structure, or othermemory cell structures.

Each of select gates 260, 261, and 262 can operate as a switch (e.g., afield-effect transistor (FET) structure. Thus, each of select gates 260,261, and 262 can have a structure of a FET. Alternatively, each ofselect gates 260, 261, and 262 can have the same structure (e.g., TANOS,SONOS, or floating gate structure) as memory cells 210, 211, 212, and213.

As shown in FIG. 3, each of select lines 280, 281, and 282 is a piece(e.g., a single layer) of conductive material (e.g., polysilicon, metal,or other conductive materials). A select line (e.g., select line 280,281, or 282) can carry a signal (e.g., signal SGD1, SDG2, or SGS) but itdoes not operate like a switch (e.g., a transistor). A select gate(e.g., select gate 260, 261, and 262 can include a portion of arespective select line (e.g., a portion of the piece of the conductivematerial that forms the respective select line) and additionalstructures to perform a function (e.g., function of a transistor). Forexample, each of select gate 260 can include a portion of select line280 and a portion of a structure (not shown) along pillar 331 adjacentselect line 280; select gate 261 can include a portion of select line281 and a portion of a structure (not shown) along pillar 331 adjacentselect line 281; and select gate 262 can include a portion of selectline 282 and a portion of a structure (not shown) along pillar 332adjacent select line 282.

Memory device 200 can include conductive segments 220 z, 221 z, 222 z,and 223 z (e.g., vertical segments extending in the z-direction) andcontacting respective access lines 220, 221, 222, and 223 and respectiveconductive contacts 220 c, 221 c, 222 c, and 223 c. Pillars 240 p, 241p, 242 p, and 243 p of respective drivers 240, 241, 242, and 243 can becoupled to respective access lines 220, 221, 222, and 223 throughrespective conductive contacts 220 c, 221 c, 222 c, and 223 c andrespective conductive segments 220 z, 221 z, 222 z, and 223 z.

As shown in FIG. 3, control gate 251 through 256 of respective drivers240, 241, 242, and 243 can be located in different levels of memorydevice 200 over (above) the levels where memory cells 210, 211, 212, and213 are located. Control gates 251 through 256 can include conductivematerials (a group of conductive materials), which can includeconductively doped polysilicon (e.g., n-type or p-type polysilicon),metals, or other conductive materials. Memory device 200 can includedielectric materials (e.g., not labeled), interleaved with (located inthe spaces between) control gates 251 through 256. Examples of suchdielectric materials include silicon dioxide.

Each of pillars 240 p, 241 p, 242 p, and 243 p can have length extendingin the z-direction (e.g., extending vertically with respect to substrate390) through control gates 251 through 256 and through the dielectricmaterials (e.g., silicon dioxide) that are interleaved with controlgates 251 through 256.

Memory device 200 can include conductive regions 240 v, 241 v, 242 v,and 243 v that can be parts of conductive materials (e.g., conductivelydoped polysilicon, metal, or other conductive materials) that form partsof respective access lines (e.g., global access lines) 220′, 221′. 222′,and 223′. Although not shown in FIG. 3, memory device 200 can includeconductive connections (which can be part of access lines 220′, 221′,222′, and 223′) that can be formed to provide electrical connectionsbetween respective pillars 240 p, 241 p, 242 p, and 243 p and voltagecontrol circuitry 248. As described above with reference to FIG. 2,voltage control circuitry 248 (e.g., formed in substrate 390 of FIG. 3)can operate to apply different voltages to access lines 220, 221, 222,and 223 (through respective pillars 240 p, 241 p, 242 p, and 243 p whendrivers 240 through 243 are turned on (e.g., concurrently turned on)).

As shown in FIG. 3, each of pillars 240 p, 241 p, 242 p, and 243 p canbe located between (and can contact) a respective conductive regionamong conductive regions 240 v, 241 v, 242 v, and 243 v and a respectiveconductive contact among conductive contacts 220 c, 221 c, 222 c, and223 c. For example, as shown in FIG. 3, pillar 240 p can be locatedbetween conductive region 240 v and conductive contact 220 c, in whichportion 240 d contacts (e.g., directly coupled to) conductive region 240v, and portion 240 s of pillar 240 p contacts (e.g., directly coupledto) conductive contact 220 c. Similarly, each of pillars 241 p, 242 p,and 243 p can have respective portion 240 d contacting a respectiveconductive region (among respective conductive regions 241 v, 242 v, and243 v) and a respective portion 240 s contacting a respective conductivecontact (among conductive contacts 221 c, 222 c, and 223 c).

Memory device 200 can include connections (conductive connections thatcan include conductive segments 251 z through 256 z, 251 x through 256x, and 256 u) to form conductive paths between control gates 251 through256 and gate control circuitry 247. For example, memory device 200 caninclude a conductive connection (between control gate 256 and gatecontrol circuitry 247) that can include conductive segments 256 z (e.g.,vertical segment in the z-direction), 256 x (e.g., horizontal segment inthe x-direction, and 256 u (e.g., vertical segments in the z-direction).Other connections between control gates 251 through 255 are shown inFIG. 3. Memory device 200 can include conductive segments 251 z through255 z (hidden from the view of FIG. 3), which are similar to conductivesegment 256 z, coupled to respective control gates 251 through 255.

FIG. 3 shows example structures (e.g., a staircase structure at edges)of control gates 251 through 256. However, in an alternative structureof memory device 200, control gates 251 through 256 may have otherstructures as long as conductive connections (e.g., connections similarto connections formed by conductive segments 251 z through 256 z, 251 xthrough 256 x, and 256 u) can be formed to provide electricalconnections between respective control gates 251 through 256 and gatecontrol circuitry 247. Moreover, FIG. 3 shows an example where controlgates 251 through 256 are located above memory cells 210, 211, 212, and213 (and above access lines 220, 221, 222, and 223). However, controlgates 251 through 256 can be located below memory cells 210, 211, 212,and 213. Further, FIG. 3 shows an example where pillars 240 p, 241 p,242 p, and 243 p of drivers 240 through 243 are vertically located(e.g., having a length in the z-direction) above memory cells 210, 211,212, and 213. In an alternative structure of memory device 200, pillars240 p, 241 p, 242 p, and 243 p can be horizontally located (e.g., havinga length in the x-direction or y-direction) in memory device 200.

FIG. 4 shows a top view of a structure of the portion of memory device200 including the portion shown in FIG. 3, according to some embodimentsdescribed herein. FIG. 4 shows example structures and routing paths ofconnections (e.g., connections including conductive segments 251 zthrough 256 z, 251 x through 256 x, and 251 z through 256 u) associatedwith drivers 240, 241, 242, and 243. However, in an alternativestructure of memory device 200, the structures and routing paths ofconnections associated with drivers 240, 241, 242, and 243 can bedifferent from those shown in FIG. 3 and FIG. 4.

As shown in FIG. 4, pillars 240 p, 241 p, 242 p, and 243 p (andassociated portions 240 d, 241 d, 242 d, and 243 d) can be separatedfrom each other in the x-direction. Conductive regions 240 v, 241 v, 242v, and 243 v (contacting respective portions 240 d, 241 d, 242 d, and243 d) can be parts of respective conductive materials (e.g., conductivelines) that can extend in the y-direction. Conductive segments 251 zthrough 256 z (coupled to respective control gates 251 through 256) canbe arranged in the x-direction and y-direction as shown in FIG. 4.Conductive segment 251 x through 256 x can be part of respectiveconductive materials that can extend in the x-direction, which isperpendicular to the y-direction. Conductive segments 251 u through 256u (underneath respective conductive segments 251 z through 256 z) can bespaced apart in the y-direction. FIG. 3 and FIG. 4 shows each of drivers240, 241, 242, and 243 includes one pillar (e.g., one of pillars 240 p,241 p, 242 p, and 243 p). However, each of drivers 240, 241, 242, and243 can include multiple pillars.

FIG. 5 shows a structure of a portion of driver 240 of memory device 200of FIG. 2, FIG. 3, and FIG. 4, according to some embodiments describedherein. For simplicity, only one of the drivers (e.g., driver 240) ofmemory device 200 is described in detail in this description. Each ofother drivers 241, 242, and 243 has a structure similar to the structureof driver 240 shown in FIG. 4.

As shown in FIG. 5, control gates 251 through 256 (e.g., a group ofconductive materials that form control gates 251 through 256) can beinterleaved with a group of dielectric materials 513 (oxide materialsare shown as an example for dielectric materials 513). Pillar 240 p cancontact conductive region 240 v and conductive contact 223 c at portions240 d and 240 s, respectively.

Driver 240 can include dielectric material 513 between pillar 240 p andcontrol gates 251 through 256 and surrounding pillar 240 p. Driver 240can also include additional dielectric material (e.g., silicon dioxide)material surrounding portion 240 d, and additional dielectric material(e.g., silicon dioxide) surrounding portion 240 s. As shown in FIG. 5,portion 240 d can contact conductive region 240 v, and portion 240 s cancontact conductive contact 220 c.

FIG. 5 (and in FIG. 6, FIG. 7, and FIG. 8) shows an example where thedielectric material between pillar 240 p and control gates 251 through256 being an oxide material (e.g., silicon dioxide (gate oxide)).However, the dielectric material between pillar 240 p and control gates251 through 256 can be different from silicon dioxide material. Examplesof such dielectric material include high-k materials (materials having adielectric constant higher than the dielectric constant of silicondioxide, e.g., nitride, AlO, HfO, ZrO and other high-K materials).Alternatively, the dielectric material between pillar 240 p and controlgates 251 through 256 can be a combination of high-K materials andsilicon dioxide material.

Pillar 240 p can be asymmetrically configured, such that portions 240 d,240 a, 240 b, and 240 s can have the same material (e.g., polysilicon)but different doping concentration. The asymmetrical properties ofpillar 240 p can enhance operations of driver 240 and allow driver 240to have improvements over some conventional drivers, as furtherdiscussed below.

In FIG. 5, portion 240 a can have a doping concentration less than(e.g., 10 to 40 times less than) the doping concentration of each ofportions 240 d and 240 s. Portion 240 b can be undoped or dopedpolysilicon. Portion 240 b can have a doping concentration less than orclose to (e.g., equal to) the doping concentration of portion 240 a ifportion 240 b is doped.

As an example, portions 240 d, 240 a, and 240 s be polysilicon dopedwith impurities (e.g., dopants) in which portion 240 d can have a dopingconcentration in the range of xe19 to xe21 per cm³ (where x is a numbergreater than zero and less than 10), portion 240 a can have a dopingconcentration in the range of xe17 to xe18 per cm³, and portion 240 scan have a doping concentration in the range of xe19 to xe21 per cm³. Inthis example, portion 240 b can have a doping concentration close to(e.g., equal to) or less than the doping concentration of portion 240 a,or alternatively, portion 240 b can be undoped polysilicon.

As shown in FIG. 5, portion 240 d has a vertical dimension (e.g., alength in the z-direction between conductive region 240 v and portion240 a). Portion 240 a has a vertical dimension (e.g., a length in thez-direction between portion 240 d and 240 b). The vertical dimension ofportion 240 a can be greater than the vertical dimension of portion 240d.

Portion 240 a can be formed by deposition, such that the material (e.g.,lightly doped polysilicon) of portion 240 a can have a grain size ofapproximately 10 nm (nanometers) to 20 nm. In an alternative structureof memory device 200, portion 210 a can be formed by techniques such asmetal-induced crystallization, laser anneal, or low-temperature anneal.In such an alternative structure, portion 240 a can include a material(e.g., a silicon-like material), in which such a material can have agrain size of approximately greater than 150 nm (e.g., a grain size ofapproximately 200 nm, which can be at least 10 times the grain size of atypical lightly doped polysilicon).

As described above with referenced to FIG. 2 through FIG. 5, driver 240can be turned on (e.g., can be placed in an on-state) to form aconductive path through pillar 240 p. Driver 240 can be turned off(e.g., can be placed in an off-state) to not form a conductive paththrough pillar 240 p. A relatively high voltage (e.g., V5=30V) can beapplied to each of control gates 251 through 256 to turn on driver 240.This can create a relatively good current path through pillar 240 p of arespective driver.

A voltage of zero volts (0V) can be applied to one or all of controlgates 251 through 256 to turn off driver 240. However, in order to allowdriver 240 to support a relatively higher breakdown voltage (e.g., abreakdown voltage BV of 30V or higher) at the area near portion 240 d(e.g., drain side of pillar 240 p) and at the area near portion 240 s(e.g., source side of pillar 240 p), voltages having different values inaddition to a voltage of 0V can be applied to control gates 251 through256 when driver 240 is placed in the off-state.

For example, during an erase operation to erase information from memorycells 210, 211, 212, and 213 (FIG. 2), a relatively high voltage (e.g.,Verase=30V) can be applied to data line 270 and line 299. This conditioncan increase the potential of pillar 240 p (FIG. 5) to approximate thevalue of voltage Verase. The increase may exceed the breakdown voltageof driver 240 and cause damage to pillar 240 p if control gates 251through 256 are improperly controlled. As described below, the structureof driver 240 in FIG. 5 allows different sets of voltages to be appliedto control gates 251 through 256 in order to reduce charging capacitance(e.g., gate-to-channel capacitance) during a write (program) operationof memory device 200 to provide support for a relatively high (e.g., 30Vor higher) breakdown voltage, and provide an improved current (e.g.,Ion) drive through pillar 240 p of driver 240.

As an example, during a write operation of memory device 200, controlgates 251 through 256 can be applied with voltages having values (e.g.,in sequentially decreasing values from control gate 251 to 256) of 10V,8V, 4V, 0V, 0V, and 0V, respectively. In another example, during anerase operation of memory device 200, control gates 251 through 256 canbe applied with voltages having values (e.g., in a sequentiallyincreasing values from control gate 251 to 256) of 0V, 0V, 9V, 16V, 23V,and 30 volts, respectively.

Thus, in a write operation the control gate (e.g., control gate 251 atthe drain side of pillar 240 p) that is closest to conductive region 240v (e.g., global word line side) can be applied with a higher voltage(e.g., 10V) than the voltage (e.g., 0V) applied to the control gate(e.g., control gate 256 at the source side pillar 240 p) that is closestto conductive contact 223 c (e.g., local word line side).

The structure of driver 240 allows it to have improvements and benefitsover some conventional drivers. For example, some conventional driversmay have a multi-gate structure. However, in such a structure, the gatesof the conventional driver may be biased at relatively high voltagevalue at the gate at the edges and a lower voltage value for the gatestoward the center in order to support a relatively high breakdownvoltage (e.g., drain side breakdown voltage of 30V or higher). Such abias scheme in the conventional driver may cause the transistorcontrolled by the edge gates to turn on, thereby increasing the totalcharging capacitance from unselected memory cell strings associated withthe conventional driver. This may make peripheral circuitry morecomplex.

In driver 240 of FIG. 5, the inclusion of portion 240 a (combined withother portions 240 d, 240 b, and 240 s) of pillar 240 p, may allowreduction in the value of the voltage (e.g., V0) applied to the controlgate (e.g., drain side edge control gate) closest to conductive region240 v (e.g., global word line side). For example, a voltage ofapproximately 10V (e.g., instead of 30V) can be applied to control gate251 (as also described above) during a write operation of memory device200. This relatively lower voltage (in comparison with the voltageapplied to the edge gate of some conventional drivers) used in driver240 can help weakly or strongly turn off the transistor control by theedge control gate, thereby reducing the total charging capacitance.

Further, during an erase operation of memory device 200, the totalcharging capacitance may have a relatively small impact in the operationof driver 240. Therefore, a relatively high voltage (e.g., 30V) can beapplied to the control gate (e.g., source side edge control gate)closest to conductive contact 223 c (e.g., local word line side). Thisallows driver 240 to have an improved current (e.g., Ion) drive

Moreover, as described above, instead of a relatively lightly dopedpolysilicon, portion 240 a can have an alternative structure, such as asilicon-like structure. Such an alternative structure can allow driver240 to achieve a higher breakdown voltage (relative to the improvedbreakdown voltage supported by driver 240) and higher current (e.g.,Ion) drive because of fewer defects, larger grains, or both, that thealternative structure (e.g., silicon-like structure) may provide.

FIG. 6 shows a structure of a portion of a driver 640, which can be avariation of driver 240 of FIG. 5, according to some embodimentsdescribed herein. Driver 640 can include elements similar to, oridentical to, the elements of driver 240 of FIG. 5. Thus, forsimplicity, similar or identical elements between drivers 240 and 640are given the same reference labels and the descriptions of suchelements are not repeated.

Differences between drivers 240 and 640 include the inclusion of adielectric material 605 located in the middle of pillar 640 in FIG. 6.Dielectric material 605 can be surrounded by portions 240 d, 240 a, 240b, and 240 s of pillar 240 p. Dielectric material 605 can includesilicon dioxide or other dielectric materials. In comparison with someconventional drivers, driver 640 can include improvements and benefitssimilar to the improvements and benefits provided by driver 240described above with reference to FIG. 5.

FIG. 7 shows a structure of a portion of a driver 740, which can be avariation of driver 240 of FIG. 5, according to some embodimentsdescribed herein. Driver 740 can include elements similar to, oridentical to, the elements of driver 240 of FIG. 5. Thus, forsimplicity, similar or identical elements between drivers 240 and 740are given the same reference labels and the descriptions of suchelements are not repeated.

Differences between drivers 240 and 740 include the inclusion of aportion 740 d that can replace portions 240 d and 240 a and portions ofdielectric material (e.g., silicon dioxide) adjacent portions 240 d and240 a of FIG. 5. Portion 740 d can include silicon dioxide or otherdielectric materials. In comparison with some conventional drivers,driver 740 can include improvements and benefits similar to theimprovements and benefits provided by driver 240 described above withreference to FIG. 5.

FIG. 8 shows a structure of a portion of a driver 840, which can be avariation of driver 740 of FIG. 7, according to some embodimentsdescribed herein. Driver 840 can include elements similar to, oridentical to, the elements of driver 740 of FIG. 7. Thus, forsimplicity, similar or identical elements between drivers 740 and 840are given the same reference labels and the descriptions of suchelements are not repeated.

Difference between drivers 740 and 840 include the inclusion ofdielectric material 805 located in the middle of pillar 640 and belowportion 740 d. Dielectric material 805 can be surrounded by portions 240b and 240 s of pillar 240 p. Dielectric material 805 can include silicondioxide or other dielectric materials. In comparisons to someconventional drivers, driver 840 can include improvements and benefitssimilar to the improvements and benefits provided by driver 240described above with reference to FIG. 5.

The illustrations of apparatuses (e.g., memory devices 100 and 200) andmethods (e.g., operating methods associated with memory devices 100 and200) are intended to provide a general understanding of the structure ofvarious embodiments and are not intended to provide a completedescription of all the elements and features of apparatuses that mightmake use of the structures described herein. An apparatus herein refersto, for example, either a device (e.g., any of memory devices 100 and200) or a system (e.g., a computer, a cellular phone, or otherelectronic systems) that includes a device such as any of memory devices100 and 200.

Any of the components described above with reference to FIG. 1 throughFIG. 8 can be implemented in a number of ways, including simulation viasoftware. Thus, apparatuses (e.g., memory devices 100 and 200 or part ofeach of these memory devices, including a control unit in these memorydevices, such as control unit 118 (FIG. 1)) described above may all becharacterized as “modules” (or “module”) herein. Such modules mayinclude hardware circuitry, single- and/or multi-processor circuits,memory circuits, software program modules and objects and/or firmware,and combinations thereof, as desired and/or as appropriate forparticular implementations of various embodiments. For example, suchmodules may be included in a system operation simulation package, suchas a software electrical signal simulation package, a power usage andranges simulation package, a capacitance-inductance simulation package,a power/heat dissipation simulation package, a signaltransmission-reception simulation package, and/or a combination ofsoftware and hardware used to operate or simulate the operation ofvarious potential embodiments.

Memory devices 100 and 200 may be included in apparatuses (e.g.,electronic circuitry) such as high-speed computers, communication andsignal processing circuitry, single- or multi-processor modules, singleor multiple embedded processors, multicore processors, messageinformation switches, and application-specific modules includingmultilayer, multichip modules. Such apparatuses may further be includedas subcomponents within a variety of other apparatuses (e.g., electronicsystems), such as televisions, cellular telephones, personal computers(e.g., laptop computers, desktop computers, handheld computers, tabletcomputers, etc.), workstations, radios, video players, audio players(e.g., MP3 (Motion Picture Experts Group, Audio Layer 3) players),vehicles, medical devices (e.g., heart monitor, blood pressure monitor,etc.), set top boxes, and others.

The embodiments described above with reference to FIG. 1 through FIG. 8include apparatuses, and methods operating the apparatuses. Some of theapparatuses include a first group of conductive materials interleavedwith a first group of dielectric materials, a first pillar extendingthrough the first group of conductive materials and the first group ofdielectric materials, memory cells located along the pillar, aconductive contact coupled to one of the conductive materials, and asecond pillar extending through a second group of conductive materialsand a second group of dielectric materials. The second pillar includes afirst portion coupled to a conductive region, a second portion, and athird portion, and a fourth portion coupled to the conductive contact.The second portion is located between the first and third portions. Thesecond portion has a doping concentration less than a dopingconcentration of each of the first and fourth portions. Otherembodiments including additional apparatuses and methods are described.

In the detailed description and the claims, a list of items joined bythe term “one of” can mean any of the listed items. For example, ifitems A and B are listed, then the phrase “one of A and B” means A onlyor B only. In another example, if items A, and C are listed, then thephrase “one of A, B and C” means A only; B only; or C only. Item A caninclude a single element or multiple elements. Item B can include asingle element or multiple elements. Item C can include a single elementor multiple elements.

In the detailed description and the claims, a list of items joined bythe term “at least one of” can mean any combination of the listed items.For example, if items A and B are listed, then the phrase “at least oneof A and B” means A only; B only; or A and B. In another example, ifitems A, and C are listed, then the phrase “at least one of A, B and C”means A only; B only; C only; A and B (excluding C); A and C (excludingB); B and C (excluding A); or all of A, B, and C. Item A can include asingle element or multiple elements. Item B can include a single elementor multiple elements. Item C can include a single element or multipleelements.

In the detailed description and the claims, a list of items joined bythe term “one of” can mean only one of the list items. For example, ifitems A and B are listed, then the phrase “one of A and B” means A only(excluding B), or B only (excluding A). In another example, if items A,B, and C are listed, then the phrase “one of A, B and C” means A only; Bonly; or C only. Item A can include a single element or multipleelements. Item B can include a single element or multiple elements. ItemC can include a single element or multiple elements.

The above description and the drawings illustrate some embodiments ofthe inventive subject matter to enable those skilled in the art topractice the embodiments of the inventive subject matter. Otherembodiments may incorporate structural, logical, electrical, process,and other changes. Examples merely typify possible variations. Portionsand features of some embodiments may be included in, or substituted for,those of others. Many other embodiments will be apparent to those ofskill in the art upon reading and understanding the above description.

What is claimed is:
 1. An apparatus comprising: a conductive regionlocated on a first level of the apparatus; a conductive contact locatedon a second level of the apparatus; a group of conductive materialsinterleaved with a group of dielectric materials, the group ofconductive materials and the group of dielectric materials located inrespective levels of the apparatus between the first and second levels;a pillar coupled between the conductive region and the conductivecontact, the pillar extending through the group of conductive materialsand the group of dielectric materials, the pillar including polysilicon;and an additional dielectric material extending through the group ofconductive materials and the group of dielectric materials, theadditional dielectric material being between the pillar and each of thegroup of conductive materials and the group of dielectric materials, andthe additional dielectric material contacting the polysilicon materialof the pillar and contacting the group of conductive materials and thegroup of dielectric materials.
 2. The apparatus of claim 1, wherein thedielectric material is silicon dioxide.
 3. The apparatus of claim 1,wherein the dielectric material is silicon nitride.
 4. The apparatus ofclaim 1, wherein the dielectric material has a dielectric constanthigher than the dielectric constant of silicon dioxide.
 5. An apparatuscomprising: a conductive region located on a first level of theapparatus; a conductive contact located on a second level of theapparatus; a group of conductive materials interleaved with a group ofdielectric materials, the group of conductive materials and the group ofdielectric materials located in respective levels of the apparatusbetween the first and second levels; a pillar coupled between theconductive region and the conductive contact, the pillar extendingthrough the group of conductive materials and the group of dielectricmaterials, the pillar including polysilicon; and an additionaldielectric material extending through the group of conductive materialsand the group of dielectric materials, the additional dielectricmaterial being between the pillar and each of the group of conductivematerials and the group of dielectric materials, and the additionaldielectric material contacting the polysilicon material of the pillar,wherein the pillar includes a first portion, a second portion, and athird portion, and a fourth portion, the second and third portionslocated between the first and fourth portions, and the second portionlocated between the first and third portions, wherein: the first portionis contacting the conductive region; the fourth portion is contactingthe conductive contact; and the second portion has a dopingconcentration less than a doping concentration of each of the first andfourth portions.
 6. The apparatus of claim 5, wherein the third portionhas a doping concentration less than the concentration of the secondportion.
 7. The apparatus of claim 5, wherein the second portion isdoped poly silicon.
 8. The apparatus of claim 5, wherein the thirdportion is doped polysilicon.
 9. The apparatus of claim 5, wherein thethird portion is undoped poly silicon.
 10. The apparatus of claim 5,wherein the first portion has a first length, the second portion has asecond length, and the second length is greater than the first length.11. The apparatus of claim 5, wherein second portion has a grain sizegreater than 150 nanometers.
 12. The apparatus of claim 5, wherein thepillar includes a dielectric, and the polysilicon material of the pillarat the third portion surrounds the dielectric.
 13. The apparatus ofclaim 12, wherein the dielectric is a first dielectric, the pillarincludes a second dielectric, and the polysilicon material of the pillarat the second portion surrounds the second dielectric.
 14. The apparatusof claim 13, wherein the pillar includes a third dielectric, and thepolysilicon material of the pillar at the third portion surrounds thethird dielectric.
 15. An apparatus comprising: a conductive regionlocated on a first level of the apparatus; a conductive contact locatedon a second level of the apparatus; a group of conductive materialsinterleaved with a group of dielectric materials, the group ofconductive materials and the group of dielectric materials located inrespective levels of the apparatus between the first and second levels;and a pillar extending through a second group of conductive materialsand a second group of dielectric materials, the pillar including: afirst portion, a second portion, and a third portion, and a fourthportion, the second and third portions located between the first andfourth portions, and the second portion located between the first andthird portions, wherein, the first portion is coupled to a conductiveregion, and the fourth portion is coupled to the conductive contact, andthe second portion has a doping concentration less than a dopingconcentration of each of the first and fourth portions.
 16. Theapparatus of claim 15, wherein the first portion has a first length, thesecond portion has a second length, and the second length is greaterthan the first length.
 17. The apparatus of claim 16, wherein the thirdportion has a doping concentration less than the concentration of thesecond portion.
 18. An apparatus comprising: a first group of conductivematerials interleaved with a first group of dielectric materials; afirst pillar extending through the first group of conductive materialsand the first group of dielectric materials; memory cells located alongthe first pillar; a conductive contact coupled to a conductive materialof the first group of conductive materials; a second pillar coupled tothe conductive contact and a conductive region, the second pillarextending through a second group of conductive materials and a secondgroup of dielectric material, the second pillar including polysilicon;and an additional dielectric material extending through the second groupof conductive materials and the second group of dielectric materials,the additional dielectric material being between the second pillar andeach of the second group of conductive materials and the second group ofdielectric materials, and the additional dielectric material contactingthe polysilicon material of the second pillar and contacting the secondgroup of conductive materials and the second group of dielectricmaterial.
 19. An apparatus comprising: a first group of conductivematerials interleaved with a first group of dielectric materials; afirst pillar extending through the first group of conductive materialsand the first group of dielectric materials; memory cells located alongthe first pillar; a conductive contact coupled to a conductive materialof the first group of conductive materials; a second pillar coupled tothe conductive contact and a conductive region, the second pillarextending through a second group of conductive materials and a secondgroup of dielectric material, the second pillar including polysilicon;and an additional dielectric material extending through the second groupof conductive materials and the second group of dielectric materials,the additional dielectric material being between the second pillar andeach of the second group of conductive materials and the second group ofdielectric materials, and the additional dielectric material contactingthe polysilicon material of the second pillar, wherein the second pillarincludes a first portion, a second portion, and a third portion, and afourth portion, the second and third portions located between the firstand fourth portions, and the second portion located between the firstand third portions, wherein: the first portion is contacting theconductive region; the fourth portion is contacting the conductivecontact; and the second portion has a doping concentration less than adoping concentration of each of the first and fourth portions.
 20. Theapparatus of claim 19, wherein the third portion has a dopingconcentration less than the concentration of the second portion.